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Investments in Unconsolidated Entities - Narrative (Details) - Tuckerman Capital Fund III, L.P. - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended |
--- | --- | --- | ---
Sep. 30, 2018 | Jun. 30, 2018 | Jun. 30, 2017 | Sep. 30, 2018 | Jun. 30, 2018 | Jun. 30, 2017 | Dec. 31, 2017
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |
Unrealized investment gains | $ 4.2 |  |  | $ 8.1 |  |  |
Total net income |  | $ 31.9 | $ 3.2 |  | $ 43.7 | $ 7.1 |
Total assets |  | $ 61.9 |  |  | $ 61.9 |  | $ 21.8

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